Mammotrophic effect of prolacting enhanced by throidectomy

Abstract

The role of thyroid hormones in relation to mammary gland structure and function has received sporadic attention. It has been shown in the rat that thyroid hormones are not necessary for mammary development and that in ovariectomised, adrenalectomised, hypophysectomised rats, prolactin and growth hormone are the principal hormones responsible for lobulo-alveolar growth. The slight stimulatory effect of thyroid hormones on mammary growth and lactation in animals has been attributed to their general metabolic effects. There are, however, a few contrary reports in the literature describing greater mammary development in rats rendered hypothyroid, which have remained unexplained. The present study was undertaken to clarify the relationship between thyroid hormones and mammary growth, with special reference to prolactin. Interest in this field was primarily aroused by several clinical and epidemiological reports associating thyroid hypofunction with breast cancer.